It has long been known that improper physical movement, especially when repeated, can result in injury to a person. This injury may manifest itself in a wide range of symptoms anywhere from sore or bruised muscles to chronic, debilitating loss of movement. In order to study and better understand safe human movement which does not result in injury, a variety of sensing, monitoring, and notification devices have been created. In general, these devices fall under the general category of range of motion (ROM) detectors.
Several such inventions have been patented to measure the range of motion of various joints of the human body for both medical studies and industry applications. Typically, these inventions require that two people simultaneously use the device: the patient/wearer and the operator of the device. The purpose of these devices is to quantitatively determine a range of motion of a human joint in angular degrees as exemplified by U.S. Pat. Nos. 4,665,928; 5,042,505; and 5,373,858. Although the devices disclosed in these patents serve the purposes for which they are intended, they do not warn the device wearer when the wearer is nearing, or has reached, a potentially dangerous angle of movement.
Another class of ROM devices has attempted to provide a warning to the wearer through an audible alarm or flashing light. Typically, these devices activate the alarm when a predetermined angle of flexion or extension has been exceeded in order to try and reduce the number of injuries that can occur as a result of the improper movement. Because of the general weakness of the human spine and back muscles, most of these devices are geared toward detecting improper torso movement while lifting an object. One such invention described in U.S. Pat. No. 5,128,655 uses a mercury switch set at a predetermined angle to trigger a counting mechanism in order to count the number of times the predetermined angle is exceeded during forward bending. Another such device described in U.S. Pat. No. 5,398,697 uses a "T" shaped collimated light beam to detect both forward and lateral bending of the spine. However, these devices are not convenient to operate and serve to merely report rather than analyze the information detected.
Training an individual to make proper movements requires more than just counting the number of times a predetermined angle is surpassed and warning the wearer of the incorrect movement. In order to prevent incorrect movement in hopes of reducing injuries, lost man hours, and workmen's compensation claims, a device must not only be able to record the frequency of improper movements, but also monitor the angular velocity and general tendencies of the wearer with regard to the unsafe movement habits. The angular velocity of any physical action affects the stretching and tautness of the muscle involved in the motion. Thus, information on angular velocity is important to monitoring and analyzing improper movement. Finally, the wearer must also be informed about the tendencies he has regarding his performance of a specific task. In particular, it is helpful to know whether improper movements occur more often in the morning or afternoon.